The primary mirror of the observatory gathers light from its targets, reflecting those rays onto a secondary mirror in front of it. That secondary mirror then bounces the light through a hole in the primary mirror and ultimately onto the sensors of the telescope's scientific instruments. With a primary mirror 21 feet 4 inches wide, the Webb is capable of peering at the first galaxies that formed just after the Big Bang, ones now more than 13 billion light years away. No mirror this large has ever been launched into space before--it will be folded like a drop-leaf table so that it can fit into a rocket, and then open up after launch.

The telescope is named after James E. Webb, who served as the administrator of NASA from 1961 to 1968. Under his direction, NASA took on a great challenge: fulfilling President Kennedy's pledge to land Americans on the moon by the decade's end.